Generally, a condenser microphone which has been widely used in mobile equipment or audio equipment consists of a voltage bias element, a pair of a diaphragm and a back plate for forming a capacitor which is changed corresponding to sound pressure, and a JFET for buffering an output signal. This typical condenser microphone has an assembly which is integrally assembled by inserting a diaphragm, a spacer ring, an insulating ring, a back plate, a conductive ring and a PCB into a case.
Recently, a semiconductor fabricating technology using a micromachining technology has been introduced for an integrated micro device. According to this technology which is called MEMS (Micro Electro Mechanical System), a sensor, an actuator and an electro mechanical structure can be fabricated in a μm unit using a micromachining technology which applies a semiconductor fabricating process, especially, an integrated circuit technology. A MEMS chip microphone manufactured by the micromachining technology has merits that include miniaturization, high-performance, multifunction and integration, which can be obtained through the high precision micromachining technology, and safety and reliability can be enhanced.
However, since the MEMS chip microphone manufactured by the micromachining technology should perform electrical driving and signal processing, it is required to package the microphone with another special purpose semiconductor chip device, that is, an ASIC (Application Specific Integrated Circuit).
A conventional technology for packaging a MEMS chip microphone is disclosed in U.S. Pat. No. 6,781,231 issued Aug. 25, 2004 and entitled by “Micro Electro Mechanical System Package with Environmental and Interference Shield”. The above package has a structure for adhering a cover which consists of an internal conductive layer and an external conductive layer on a multi-layered substrate which is alternately overlapped by a conductive layer and a non conductive layer using a conductive adhesive.
Thus, the conventional packaging method has problems in that a manufacturing cost is raised and a bonding property is deteriorated due to a complex process, and the method is sensitive to external noise such as an electromagnetic wave noise and the like since a non conductive material unlike a metal housing is used.